Devices and methods for use during knee replacement surgery

Abstract

A knee alignment measurement tool for use during a total knee replacement surgery may include the following main components: a sensor assembly, a display unit configured to power up, operatively control the individual sensors of the sensor assembly, and display the readings therefrom, and a flexible gooseneck cable operatively connecting the sensor assembly to the display unit. The sensor assembly may include a rigid base supporting a circuit board, a left sensor and a right sensor positioned adjacent to the left center, and a cover sealed to the rigid base to enclose the left sensor and the right sensor, wherein the cover does not abut the rigid base during the compression of the sensor assembly.

What is claimed is: 
     
         1 . A knee alignment measurement tool comprising:
 a sensor assembly comprising, in turn, a rigid base supporting a left sensor and a right sensor positioned adjacent to the left sensor, and a cover sealed to and spaced apart from the rigid base, the cover comprises at least one thicker portion configured to transmit compression force applied on top thereof without affecting remaining areas of the cover, and   a display unit operatively connected to the sensor assembly and configured to power up, operatively control the left sensor and the right sensor, and display the readings therefrom,   wherein the knee alignment measurement tool is configured to provide feedback on compression forces between components of a knee replacement prosthesis and a balance of forces between a left condyle and a right condyle.   
     
     
         2 . The knee alignment measurement instrument, as in  claim 1 , wherein the sensor assembly comprises a group of left sensors and a group of right sensors, at least one sensor of each group being configured as a primary load-bearing sensor and at least one sensor of each group being configured as a non-load-bearing sensor, the cover of the sensor assembly being configured such that no thicker portion is arranged above each non-load-bearing sensor so that no significant compressive load is transmitted thereto, and wherein control electronics are configured to monitor outputs of the non-load-bearing sensors as in situ reference signals indicative of thermal expansion and environmental effects, and to compensate outputs of the load-bearing sensors based on the reference signals so as to improve accuracy and stability of force measurement across changing operating temperatures. 
     
     
         3 . The knee alignment tool, as in  claim 1 , wherein the thicker portion of the cover is surrounded by a thinner portion forming a living hinge around the thicker portion to allow the thicker portion to transmit compression force applied on top thereof to the left sensor or the right sensor without deforming and affecting remaining areas of the cover. 
     
     
         4 . The knee alignment tool, as in  claim 1 , wherein the cover is spaced apart from the rigid base to form a predefined gap therebetween, so that the cover does not abut the rigid base during the compression of the sensor assembly. 
     
     
         5 . A knee alignment measurement instrument comprising:
 a knee alignment measurement tool of  claim 1 , further comprising a center post positioned between the left sensor and the right sensor and extending above the cover,   a femur-facing insert comprising a femoral surface configured to face a femur and to stay in contact therewith during a knee alignment measurement procedure, and   a shim configured to be inserted between the femur-facing insert and the knee alignment measurement tool while constrained by the center post thereof, wherein the shim is configured to change a distance between the femur-facing insert and the knee alignment measurement tool.   
     
     
         6 . The knee alignment measurement instrument, as in  claim 5 , wherein the shim comprises a plurality of interchangeable shims of various thicknesses, thereby inserting one shim at a time defines the distance between the femur-facing insert and the knee alignment measurement tool to correspond to a thickness of the inserted shim of the plurality of interchangeable shims. 
     
     
         7 . An inflatable shim for adjusting a distance between a femur and a tibia during a knee alignment measurement procedure, the inflatable shim is configured to form a stack with a femur-facing insert and a knee alignment measurement tool, the inflatable shim comprises an inflatable bladder and a distance sensor, wherein inflation of the inflatable bladder causes a measurable increase of a total height of the stack corresponding to a measurable increase of the distance between the femur and the tibia,
 wherein the inflatable bladder comprises, in turn, an inflation port configured to ingress and egress air in or out of the inflatable bladder, causing a corresponding change in a height thereof. 
 
     
     
         8 . The inflatable shim, as in  claim 7 , further comprising a rigid shim base having the inflatable bladder mounted thereon. 
     
     
         9 . The inflatable shim, as in  claim 8 , wherein the rigid shim base is detachable from the inflatable bladder so as to facilitate replacement of the inflatable bladder and reuse of the rigid shim base. 
     
     
         10 . A knee alignment measurement instrument comprising the inflatable shim, as in  claim 7 , wherein the knee alignment measurement tool is configured to be positioned between the inflatable shim and the femur-facing insert to form the stack of the inflatable shim, the knee alignment measurement tool, and the femur-facing insert. 
     
     
         11 . A knee alignment measurement instrument comprising the inflatable shim, as in  claim 8 , wherein the knee alignment measurement tool comprises a center post extending therefrom, the inflatable shim is configured to be positioned at least partially around the center post and between the knee alignment measurement instrument and the femur-facing insert. 
     
     
         12 . The knee alignment measurement instrument, as in  claim 10 , wherein the knee alignment measurement tool further comprises a sensor assembly comprising, in turn, a rigid base supporting a left sensor and a right sensor positioned adjacent to the left sensor, and a cover configured to transmit compression force applied on top thereof to individually the left sensor and the right sensor, and
 a display unit operatively connected to the sensor assembly and the distance sensor and configured to power up, operatively control the left sensor, the right sensor, and the distance sensor, and display the readings therefrom,   wherein the knee alignment measurement tool is configured to provide feedback on compression forces between components of a knee replacement prosthesis, a balance of forces between a left condyle and a right condyle, and the distance between the femur and the tibia.   
     
     
         13 . The inflatable shim, as in  claim 7 , wherein inflation of the inflatable bladder increases the total height of the stack from an additional 1 mm to an additional 8 mm. 
     
     
         14 . The inflatable shim, as in  claim 7 , wherein the distance sensor is a capacitive distance-measuring sensor. 
     
     
         15 . The inflatable shim, as in  claim 7 , wherein the distance sensor is a lidar sensor configured to measure the distance using a pulsed laser light. 
     
     
         16 . The inflatable shim, as in  claim 12 , wherein the inflatable bladder comprises a left balloon and a right balloon. 
     
     
         17 . The inflatable shim, as in  claim 16 , wherein when the inflatable shim is positioned between the knee alignment measurement tool and the femur-facing insert, the left balloon is shaped and aligned with the left sensor and the right balloon is shaped and aligned with the right sensor, thereby inflation of the inflatable bladder causes a corresponding transmission of compression forces from the left ballon to the left sensor and from the right balloon to the right sensor. 
     
     
         18 . The inflatable shim, as in  claim 16 , wherein the left balloon and the right balloon each comprise or is operatively connected to a pressure sensor configured to measure the internal air pressure within the respective balloon, and wherein the pressure measured in the left balloon corresponds to the compressive force applied to the medial compartment of the knee joint and the pressure measured in the right balloon corresponds to the compressive force applied to the lateral compartment of the knee joint, thereby enabling the display unit to calculate both total joint force and medial-lateral force balance from the pressure readings of the left balloon and the right balloon without requiring separate solid-state force sensors within the sensor assembly.